Clintons finally decide to join Obama campaign as he starts to look unstoppable

Barack Obama was expected to get a boost today when former President Bill Clinton and his wife, Senator Hillary Clinton, begin making joint campaign appearances on his behalf.

The nation's best known and most powerful Democrats for nearly two decades will be on the road for Obama, who vanquished Hillary Clinton last spring in a bitter primary contest.

The Clintons apparently have put that behind them and will stump for Obama's election as he pulls ahead in the national polls.

The Clintons are now making public appearances to support Barack Obama and his running mate Joe Biden. (From left) Biden, his wife Jill and Hillary and Bill Clinton on the campaign trail in Scranton, Pennsylvania

Hillary Clinton speaks to the crowd of supporters at the rally

They are to appear with Obama's running mate, Joe Biden, at a rally this afternoon in the working class town of Scranton, Pennsylvania.

The location is meaningful because Biden was born in Scranton and lived there for several years as a child, while Hillary Clinton's father grew up in the town and is buried there.

On Saturday, Republican presidential candidate John McCain toned down his rhetoric against Obama, apparently concerned with angry sloganeering from supporters at some of his rallies - and criticism that he had gone too far.

Obama, in turn, made a slight nod to McCain as he campaigned in Philadelphia and asked voters to have faith in him as the next president.

Clinton waves to cheering supporters as he prepares to take the stage at the University of Central Florida

Even as he criticized McCain's economic proposals, Obama acknowledged that the Republican nominee has begun to ask his supporters to temper their attacks on him.

'I appreciated his reminder that we can disagree while still being respectful of each other,' Obama told thousands of supporters at the first of four outdoor rallies in Philadelphia.

Police estimated he drew more than 60,000 people to the four events.

'Sen. McCain has served this country with honor,' Obama said later. 'He deserves our thanks for that.'

McCain kept his speech at a rally in Davenport, Iowa, focused on the economy and his policies, a striking change from just days ago when his campaign redoubled its challenge to Obama over his association with a former 1960s radical.

McCain also claimed that American voters did not really know Obama and his 'radical' views.

US Senator and Democratic presidential candidate Barack Obama speaks during a rally in Indianapolis, Indiana

The tone at McCain's and running mate Sarah Palin's events during the past week had been turning toward the sour as disappointed supporters see his presidential campaign lag against Obama.

Angry Republicans had shouted 'terrorist' and 'off with his head' at the mention of Obama's connections to former Weather Underground member William Ayers, whose group bombed federal buildings in protest of the Vietnam War when Obama was a child.

The two had worked together on community projects in Chicago, and Obama has denounced Ayers' violent past.

On Friday during a town hall-style meeting in Lakeville, Minnesota, a supporter told McCain that he feared what would happen if Obama were elected. McCain drew boos when he defended his rival as a "decent person and a person that you do not have to be scared of as president of the United States."

McCain returned to that note of civility on Saturday as his quandary became clearer: He needed to excite his party's base without inciting them, challenge Obama while being an honorable opponent, and find a game-changing strategy for his faltering campaign without crossing the line.

Fury: A John McCain supporter yells at Obama supporters before a rally in Strongsville, Ohio

When an anti-war protester interrupted him, McCain nervously watched what the crowd would do. The protester was hoisted on shoulders and McCain's supporters chanted'We want John'.

'As people are trying to stay in their homes, keep their jobs and afford health care, is what they want for us, to yell at each other?' he asked. 'No. They want us to sit down together, Republican and Democrat, to work through this terrible time of crisis.'

In a statement issued Saturday, Representative John Lewis, a Georgia Democrat and veteran of the civil rights movement, charged that the negative tone of the Republican presidential campaign reminded him of the hateful atmosphere that segregationist Governor George Wallace fostered in Alabama in the 1960s.

Lewis, who is black, accused McCain and Palin of 'sowing the seeds of hatred and division, and there is no need for this hostility in our political discourse'.

McCain on Saturday called Lewis' remarks 'shocking and beyond the pale'.

Late on Saturday, Lewis released another statement saying it was not his 'intention or desire' to directly compare McCain or Palin to Wallace.

'My statement was a reminder to all Americans that toxic language can lead to destructive behavior,' he said.

'I am glad that Senator McCain has taken some steps to correct divisive speech at his rallies. I believe we need to return to civil discourse in this election about the pressing economic issues that are affecting our nation.'

The Republican vice presidential candidate, Alaska Governor Sarah Palin, also campaigned in Pennsylvania on Saturday. She attacked Obama on abortion at a rally in Johnstown, saying the Democratic candidate has 'left behind even the middle ground on the issue of life'.

Palin said she and McCain would be 'defenders of the culture of life'.

She opposes abortion in all cases except where the pregnancy threatens the woman's life. McCain would also allow abortion in cases of rape or incest.

Palin said it was about time that Obama was 'called' on his abortion views which she called 'radical'.

'Please, it is not negative and it's not mean-spirited to talk about his record,' she said.Obama favors abortion rights.

Defying tradition in Republican-leaning states, Obama said, he is leading McCain in Montana and North Carolina. His lead in Virginia, which Democrats last carried in 1964, is 6 or 7 percentage points, he told the donors.

Democrats have carried Pennsylvania in recent presidential elections, although sometimes narrowly. McCain has campaigned aggressively in the state, but polls show Obama leading.

John McCain (R) and running-mate Sarah Palin address a rally at Lehigh University in Bethlehem, Pennslyvania